This project will investigate the development of infants' perceptions of affective expressions. An emphasis is placed on infants' detection of invariant relations dynamic, multimodally-presented expressive behaviors as potential information for the meaning of those expressions. Five experiments are proposed. These concern infants' perception of invariant intermodal relations in bimodally-presented expressions, their detections and generalization of information for a single expression across persons, and their ability to discriminate ongoing vocal expressions. Infants of three, five and seven months will be included in order to determine whether there are any development trends in infants' abilities to discriminate and recognize expressions, and whether there are any systematic differences in their preferences for specific expressions. Visual preference, habituation of looking, and cross-modal habituation methods will be used. The project is concerned with the development of behavior as determined by psychological factors, particularly as it applies to how the developing infant abstracts and uses information in expressive behaviors to understand their meaning.